The gelling characteristics of whey proteins is governed by factors which affect the structural properties of the protein. To understand this structure gelling relationship, the following factors were investigated; protein concentration, heating temperature and time, pH, NaCl and sugars. The effect of these factors on the molecular structure and gelatin properties of whey protein concentrate (WPC), $ beta$-lactoglobulin ($ beta$-lg), $ alpha$-lactalbumin ($ alpha$-lac) and bovine serum albumin (BSA) were studied using polyacrylamide gel electrophoresis, HPLC, mass spectrometry, differential scanning calorimetry and Fourier transform infrared spectroscopy. The results showed that protein concentration affected textural properties without affecting the molecular structure of the whey proteins while heating temperature, pH and NaCl affected both molecular structure and the textural characteristics. NaCl and sugars increased the stability of whey proteins to thermal denaturation but decreased gel formation. $ beta$-lg formed an opaque gel at pH 3 and a translucent gel at pH 9; the peak temperature of denaturation was 84$ sp circ$C at pH 3 and 70$ sp circ$C at pH 9. At both acid and alkaline pH, denaturation of $ beta$-lg resulted in the formation of intermolecular $ beta$-sheet structures associated with aggregation. These $ beta$-sheet aggregate structures were also observed when $ alpha$-lac was heated at pH 3 and 5 but not at pH 7 and 9. At pH 7, heating $ alpha$-lac resulted in a loss of $ alpha$-helix, $3 sb{10}$-helix and $ beta$-sheet and an increase in turns. DSC showed two reversible transitions at 39.6$ sp circ$C (A) and 64.8$ sp circ$C (B). At pH 3, transition A was partially reversible (14%) while transition B was completely reversible. At pH 9, transitions A and B were completely irreversible and a translucent gel was formed. Bovine serum albumin (BSA) showed maximum stability to thermal denaturation at pH 5. Denaturation of BSA resulted in the loss of $
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.28994 |
| Date | January 1995 |
| Creators | Boye, Joyce Irene Ashami |
| Contributors | Alli, Inteaz (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Food Science and Agricultural Chemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001481797, proquestno: NN08083, Theses scanned by UMI/ProQuest. |
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